Researchers now need only a blood sample from a pregnant mother to construct a fetus’ entire genome

Last month, clinicians announced that they could sequence a fetus’ entire genome by taking samples from the pregnant mother’s blood and that of the father-to-be. As if this wasn’t a big enough breakthrough for screening potential genetic diseases, researchers have taken the method a step further. Forget the father, they say: now all we need for sequencing is the mother.

The more difficult, but more complete, method uses DNA from the pregnant woman and the fetus to map out every last letter of the fetal genome. This approach has the advantage that it can pick up the 50 or so unique mutations that a fetus has but its parents do not. The sequence was 99.8 per cent accurate – a figure the researchers determined by sequencing the cord blood after the birth.

An easier but slightly less accurate second method sequences only the portions of the fetus’ genome that code for functioning proteins. Using this trick, they could sequence up to 75 percent of the fetal genome during the first trimester, and up to 99 percent by the third.

The researchers are leaning towards the second method since it’s easier to carry out and less convoluted to interpret than the full genome sequence. In future tests, they plan to refine the method to seek out a few well known diseases.

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